power supply - What would be the input current of buck regulator

I have a basic question about measuring input current. The buck regulator I have chosen is rated to deliver 3.3V/2A from +12V input. My question is -

Is the input current 2A (load current) + few mA (needs for operation)?

Or because of stepdown from 12V to 3.3V, based on load current, the input current is 500mA + few mA?

Is the 2A output current taken entirely from the input or step down conversion delivers 2A after consuming few mA.